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Subject[PATCH hyperv-fixes] hv_netvsc: Fix IP header checksum for coalesced packets
Date
From: Haiyang Zhang <haiyangz@microsoft.com>

Incoming packets may have IP header checksum verified by the host.
They may not have IP header checksum computed after coalescing.
This patch re-compute the checksum when necessary, otherwise the
packets may be dropped, because Linux network stack always checks it.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
drivers/net/hyperv/netvsc_drv.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 256adbd044f5..cf4897043e83 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -744,6 +744,14 @@ void netvsc_linkstatus_callback(struct net_device *net,
schedule_delayed_work(&ndev_ctx->dwork, 0);
}

+static void netvsc_comp_ipcsum(struct sk_buff *skb)
+{
+ struct iphdr *iph = (struct iphdr *)skb->data;
+
+ iph->check = 0;
+ iph->check = ip_fast_csum(iph, iph->ihl);
+}
+
static struct sk_buff *netvsc_alloc_recv_skb(struct net_device *net,
struct netvsc_channel *nvchan)
{
@@ -770,9 +778,17 @@ static struct sk_buff *netvsc_alloc_recv_skb(struct net_device *net,
/* skb is already created with CHECKSUM_NONE */
skb_checksum_none_assert(skb);

- /*
- * In Linux, the IP checksum is always checked.
- * Do L4 checksum offload if enabled and present.
+ /* Incoming packets may have IP header checksum verified by the host.
+ * They may not have IP header checksum computed after coalescing.
+ * We compute it here if the flags are set, because on Linux, the IP
+ * checksum is always checked.
+ */
+ if (csum_info && csum_info->receive.ip_checksum_value_invalid &&
+ csum_info->receive.ip_checksum_succeeded &&
+ skb->protocol == htons(ETH_P_IP))
+ netvsc_comp_ipcsum(skb);
+
+ /* Do L4 checksum offload if enabled and present.
*/
if (csum_info && (net->features & NETIF_F_RXCSUM)) {
if (csum_info->receive.tcp_checksum_succeeded ||
--
2.19.1
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